Abrasive detergent applicators and compositions have been developed to facilitate the removal of tenacious soils such as dried and burned food residues on kitchenware, chemical residues in laboratory equipment, coatings of rust and other corrosion and the like. Abrasive detergent applicators often involve the use of metal or hard plastic sheets or pads which are impregnated with detergents, builder salts and bleaches. However, the detergent reservoirs in these applicators are rapidly depleted and the substrates are themselves subjected to chemical and physical degradation. Furthermore, it is not possible for the user to control the amount of detergent which is applied from the substrate onto the target surface.
Detergent compositions have been disclosed which include varying amounts of particulate abrasive solids, such as powdered minerals. These compositions can be formulated as liquid suspensions or as semi-liquid pastes. Although relatively large amounts of abrasives can be included in such compositions, liquid products are difficult to manually apply in a controlled fashion and both liquid and pasty detergent compositions tend to lack adequate phase stability.
For example, Chapman (U.S. Pat. No. 4,240,919) discloses a thixotropic liquid detergent composition which employs multivalent metal stearate soaps to hold the abrasive particles in suspension. Kiewart et al. (U.S. Pat. No. 4,122,025) discloses pourable or pasty cleaning compositions containing low density cristobalite abrasive particles which allegedly resist settling.
A persistent problem associated with many of these products is that they are overly abrasive. The particulate abrasive particles exhibit a high coeffient of friction, which creates drag, and makes the products difficult to apply. This high coefficient of friction also makes the products difficult to remove from the target surface after use. Furthermore, high-solids abrasive detergent products are generally designed for cleaning kitchenware such as soiled metal pots and pans. In recent years, a wider variety of materials have been used to make cooking utensils, including plastics and specially coated and plated metals. Thus, a need exists for highly abrasive detergents which will effectively clean such utensils without dulling or abrading the surfaces thereof.
Because these properties are somewhat at odds, it is often necessary to limit the amount of abrasive material or to employ mild abrasives in order to avoid such damage. For example, Dawson (U.S. Pat. No. 4,537,604), discloses paste detergent compositions comprising abrasive particles formed by agglomerating mineral particles with organic binders. Although such agglomerates may moderate the abrasive power of the mineral particles included therein, their preparation necessarily complicates the formulation of these detergents, and increases their cost.
From the foregoing, it is clear that a need exists for a high solids detergent composition which is phase stable under a wide range of conditions, and is easy to apply and remove while retaining high cleaning power.